Due to the introduction of individually optimized spectacle lenses, it is possible to deal with the requirements of people having vision errors and, for example, provide spectacle lenses having individually optimized visual ranges. Custom-fitted spectacle lenses make it possible to make an optimal correction of the optical defects of the vision of a wearer of spectacle lenses. Individual calculation and adaptation of spectacle lenses is also possible for sports spectacles, which are distinguished by large deflections, bow angles, and pantoscopic angles.
To completely exhaust the optical advantages of individual spectacle lenses, in particular of individually adapted progressive power lenses, it is necessary to calculate and produce these spectacle lenses knowing the wearing position of the user and to wear them in accordance with the wearing position used for calculation and production. The wearing position is a function of multiple parameters, for example, the interpupillary distance, the bow angle, the spectacle lens pantoscopic angle, the spectacle frame, the corneal vertex distance of the system of spectacles and eye, and the grinding height of the spectacle lenses. These and further parameters, which may be used and/or are necessary for describing the wearing position, are contained in relevant standards, such as DIN EN ISO 1366, DIN 58 208, DIN EN ISO 8624, and DIN 5340 and may be taken therefrom. Furthermore, it is necessary for the spectacle lenses to be situated and/or centered in a spectacle frame in accordance with the optical parameters which were used for the production, so that the spectacle lenses are actually worn in accordance with the optical parameters in the wearing position.
Multiple measuring devices are available to the optician for determining the individual optical parameters. For example, the optician may analyze pupillary reflexes using a so-called pupillometer and/or determine the distance of the pupil centers to ascertain the interpupillary distance in this way.
Pantoscopic angle and corneal vertex distance may be determined using a measuring device in which, in the habitual head and body posture of the customer, the measuring device is held on a frame plane of a spectacle frame. The pantoscopic angle may be read off laterally via a gravity-driven pointer on the basis of a scale. An engraved ruler is used for determining the corneal vertex distance, using which the distance between the estimated groove base of the spectacle frame and the cornea is also measured from the side.
The bow angle of the spectacle frame may be determined using a measuring device on which the pair of spectacles is laid. The nasal edge of an optic disk has to be situated over a pivot point of a movable measuring arm, the other optic disk running parallel to an engraved line. The measuring arm is set in such a way that a marked axis of the measuring arm runs parallel to the frame plane of the optic disk lying above it. The bow angle may subsequently be read off a scale.
It is an object of the present invention to provide a possibility for precisely determining optical parameters of a user in a simple way.
This object is achieved by the device according to Claim 1, the device according to Claim 27, the method according to Claim 28, and the computer program according to Claim 31. Preferred embodiments and/or variations are the subject matter of the dependent claims.
According to one aspect of the present invention, a device according to the present invention for determining optical parameters of a user comprises                at least two image recording units, which are designed and situated to generate image data of at least sub-sections of the head of the user;        a data processing unit having                    a user data determination unit, which is designed to determine user data of at least one sub-section of the head or at least one sub-section of a system of the head and a pair of spectacles of the user situated thereon in the wearing position on the basis of the generated image data, the user data comprising location information in the three-dimensional space of predetermined points of the sub-section of the head or of the sub-section of the system and            a parameter determination unit, which is designed to determine at least one part of the optical parameters of the user on the basis of the user data;                        a data output unit, which is designed to output at least one part of the determined optical parameters of the user.        
Preferably, three-dimensional data of the sub-section of the head or the system of the head and the pair of spectacles is advantageously generated on the basis of the present device. The three-dimensional data are determined using the image data. The image data which are generated using a first image recording unit differ from the image data which are generated using a second image recording unit. The differences in the image data arise in particular because the two image recording units are preferably situated at different positions. Because of the preferably different positions of the at least two image recording units, the particular image data are generated from different perspective views of the head and/or the sub-section of the head. Coordinates in the three-dimensional space, for predetermined or predeterminable points on the head of the user or on the system of the head and the pair of spectacles, may be determined on the basis of the different perspective views and/or the different image data of the sub-section of the head thus generated, while knowing the position of the cameras in relation to one another.
Two recording units in the meaning of the present invention are two digital cameras, for example, which are positioned separately from one another. It is possible that an image recording unit preferably comprises a digital camera and at least one optical deflection element and/or mirror, the image data of the sub-section of the head being recorded and/or generated by the camera using the deflection mirror. Two image recording units therefore comprise two digital cameras in particular and at least two deflection elements or mirrors in the same way, for example, one digital camera and at least one deflection mirror representing one image recording unit in each case. Furthermore, two image recording units may preferably also comprise precisely one digital camera and two deflection elements or mirrors, image data being recorded and/or generated with a time delay using the digital camera. For example, image data are generated at a first instant, the sub-section of the head being imaged using one deflection mirror, and image data are generated at a second instant, said data imaging the sub-section of the head using the other deflection mirror. Furthermore, the camera may also be situated in such a way that image data are generated by the camera at the first or second instant, no deflection mirror being necessary and/or situated between the camera and the head.
Advantageously, a representation of at least the sub-section of the head or at least one sub-section of the system of the head and the pair of spectacles of the user situated thereon in the wearing position is determined using the device according to the present invention on the basis of two-dimensional image data. Location relations to one another in the three-dimensional space of the user data may be determined easily on the basis of this three-dimensional representation and the optical parameters of the user may be determined therefrom.
In particular, multiple optical parameters of the user necessary for describing the wearing position of a pair of spectacles and/or the spectacle lenses may advantageously be determined precisely and easily.
Furthermore, image data of sub-sections which overlap as much as possible, in particular the same sub-section of the head of the user, is generated by the two image recording units, the image recording units being designed and situated in such a way that at least one pupil of the user is completely imaged in the first image data. Furthermore, only the generated image data in which a pupil of the user is completely imaged is used for determining the user data. In particular, the same pupil of the user is completely imaged in image data which are generated by the two or more image recording units.
Furthermore, both pupils of the user may be imaged in each case in the image data of the two image recording units.
The data processing unit is preferably a computer or microprocessor. Furthermore, the user data determination unit and the parameter determination unit may operate independently of one another. Preferably, the data processing unit is designed in such a way that the user data determination unit and the parameter determination unit are operated using a microprocessor. In other words, the data processing unit is designed in such a way that a microprocessor executes both the task(s) of the user data determination unit and also those of the parameter determination unit.
Furthermore, the image recording units are preferably designed and situated in such a way that at least one pupil of the user and a pupil frame edge and/or a spectacle lens edge is imaged in the generated image data, the at least one pupil of the user being enclosed by the spectacle frame edge and/or spectacle lens edge in the generated image data.
In other words, a two-dimensional image of at least one sub-section of the head of the user is generated by each image recording unit. Each of the images contains one pupil of the user or both pupils of the user. For example, image data which have been generated by an image recording unit may only contain one pupil of the user. Image data which are generated by a further image recording unit, in contrast, contain both pupils of the user. In each case, at least one pupil is imaged and at least one spectacle frame edge and/or one spectacle lens edge is imaged in all image data used for further analysis, it being the same pupil in all of this image data. Furthermore, the spectacle frame edge or spectacle lens edge assigned to the imaged pupil is imaged. The image recording units are additionally designed and situated in such a way that the image of the pupil lies inside the image of the spectacle frame or spectacle lens edge in the two-dimensional image data. Especially preferably, the image of the pupil lies completely inside the image of the spectacle frame or spectacle lens edge.
In a further preferred embodiment of the present invention, the user data comprise location information for at least one of the following points:                intersection points of a horizontal plane in the reference system of the user with the spectacle lens edges and/or the spectacle frame edges of the spectacles, the horizontal plane of the user intersecting both pupils of the user and running parallel to a predetermined zero line of sight of the user;        intersection points of a vertical plane in the reference system of the user with the spectacle lens edges and/or the spectacle frame edges of the spectacles, the vertical plane of the user running perpendicularly to the horizontal plane of the user and parallel to the predetermined zero line of sight of the user and intersecting a pupil of the user;        at least one pupil center point;        delimitations of at least one spectacle lens of the user according to dimensioning in the boxing system;        bridge center point of the spectacle frame of the pair of spectacles.        
Dimensioning in the boxing system is understood in the meaning of the present invention as the measurement system as is described in the relevant standards, for example, in DIN EN ISO 8624 and/or DIN EN ISO 1366 and/or DIN 58 208 and/or DIN 5340. Furthermore, reference is made, in regard to the boxing system and further typical terms and parameters used, to the book “Die Optik des Auges und der Sehhilfen [The Optics of the Eye and Visual Aids]” by Dr. Roland Enders, 1995 Optische Fachveröffentlichung GmbH, Heidelberg, and the book “Optik und Technik der Brille [Optics and Technology of Spectacles]” by Heinz Diepes and Ralf Blendowksi, 2002 Verlag Optische Fachveröffentlichungen GmbH, Heidelberg. The standards and the cited books thus represent an integral part of the disclosure of the present application for the definitions of terms.
The delimitations according to dimensioning in the boxing system comprise, for example, frame points for one eye or both eyes which lie furthest to the outside or inside and/or up or down. These frame points are typically determined on the basis of tangents on the spectacle frame and/or the areas of the spectacle frame assigned to the particular eyes (compare DIN 58 208; FIG. 3).
The zero viewing direction in the meaning of the present invention is a viewing direction straight ahead with parallel visual axes. In other words, this is a viewing direction which is defined by a position of the eye in relation to the head of the user, the eyes looking at an object which is at eye height and is situated at an infinitely distant point. As a result, the zero viewing direction in the meaning of the present invention is solely determined by the position of the eyes in relation to the head of the user. If the head of the user is in a vertical upright position, the zero viewing direction essentially corresponds to the horizontal direction in the reference system of the earth. However, the zero viewing direction may be tilted in relation to the horizontal direction in the reference system of the earth, if, for example, the user inclines his head to the front or to the side without further movement of the eyes. Analogously, a plane is spanned by the zero viewing direction of both eyes which is essentially parallel to the horizontal plane in the reference system of the earth. The plane which is spanned by the two zero viewing directions of the two eyes may also be inclined to the horizontal plane in the reference system of the earth, if the user inclines his head forward or to the side, for example.
Preferably, the horizontal plane of the user corresponds to a first plane and the vertical plane of the user corresponds to a second plane which is perpendicular to the first plane. For example, the horizontal plane in the reference system of the user may be situated parallel to a horizontal plane in the reference system of the earth and only run through the center point of one pupil. This is the case in particular if the two eyes of the user are situated at different heights (in the reference system of the earth), for example.
The optical parameters of the device according to the present invention preferably comprise one of the following values:                interpupillary distance;        monocular interpupillary distance;        corneal vertex distance according to reference point requirement and/or according to eye rotation point requirement;        monocular centration distance;        centration point coordinates;        lens distance or boxed lens distance;        decentration of the centration point;        lens height and width or boxed lens height and width;        lens center distance or boxed lens center distance;        spectacle lens pantoscopic angle;        bow angle;        grinding height.        
Furthermore, the optical parameters also preferably comprise an eye rotation point of an eye and/or parameters, on the basis of which dynamic vision behavior of the user may be determined, such as convergence of an eye position and/or gaze deflection.
The interpupillary distance essentially corresponds to the distance of the pupil centers. The optical parameters comprise especially preferred physiological and anatomical parameters of a spectacle wearer, frame-specific properties, and features of a system of spectacles-eye of the user, which is described in DIN 58208, for example. The features of the system spectacles-eye of the user may be used for calculating spectacle lenses and for precise centration of spectacle lenses, for example, centration data being determined according to the cited norms exactly in relation to an optic disk or frame plane. The plane of the optic disk is the plane through a horizontal and vertical center line (in the reference system of the earth) in the right or left boxing system in the spectacle frame. The frame plane is the plane through center lines, which are vertical to one another, of the boxing systems establishing the right and left disk plane of the spectacle frame.
Furthermore, in the operating position, the image recording units are preferably situated within a spatial area which is enclosed by a cone having a predetermined aperture angle, the cone apex of the cone being situated in the surroundings of a predetermined reference point and the cone axis being situated parallel to a predetermined direction, the zero viewing direction of the user corresponding to the predetermined direction in operation.
In other words, the image recording units are preferably situated in a conical volume. The apex of the cone is located at a distance of less than 20 cm, preferably less than 10 cm, more preferably approximately 0 cm from the reference point.
Preferably, in operation, the location of one of the pupils of the user or the location of the root of the nose of the user approximately corresponds to the predetermined reference point. In operation of the device, the user may be positioned in such a way that the location of one of the pupils or the root of the nose of the user is approximately at the predetermined reference point, i.e., essentially the cone apex. The distance between the cone apex of the cone and one of the pupils and/or the root of the nose of the user is preferably less than approximately 20 cm, more preferably less than approximately 10 cm, especially preferably approximately 0 cm.
According to a further preferred embodiment of the present invention, the aperture angle of the cone is less than 90°, more preferably between approximately 60° and approximately 10°, especially preferably between approximately 45° and approximately 20°, particularly approximately 30°. The aperture angle corresponds to the angle between the axis of symmetry of the cone and the lateral surface of the cone, the cone being rotationally symmetric. In other words, the cone volume may be described by rotation of a right triangle, the triangle rotating around a cathetus and the lateral surface of the cone being described on the basis of the rotation of the hypotenuse of the right triangle. The aperture angle of the cone corresponds to the angle between the hypotenuse and the axis of rotation, i.e., the cited cathetus of the right triangle.
User data may advantageously be determined very effectively by the configuration of the image recording units on a cone having an aperture angle preferably of approximately 30°, because image data may be generated without the pupils of the user being concealed by the spectacle frame or a nose of the user, for example.
Furthermore, effective optical axes of the image recording units preferably at least approximately intersect, an intersection angle being between approximately 60° and approximately 10°, preferably between approximately 45° and approximately 20°, especially preferably approximately 30°.
Effective optical axes of the image recording units in the meaning of the present invention are those areas of lines which extend from the center point of the particular apertures of the image recording units perpendicular to these apertures and intersect the imaged sub-section of the head of the user. In other words, the effective optical axes are particularly the optical axes of the image recording units, these optical axes typically being situated perpendicular to a lens system of the image recording units and extending from the center of the lens system. If no further optical elements, such as deflection mirrors or prisms, are situated in the beam path of the image recording units, the effective optical axis essentially corresponds to the optical axis of the image recording unit. However, if further optical elements, such as one or more deflection mirrors, are situated in the beam path of the image recording unit, the effective optical axis no longer corresponds to the optical axis of the image recording unit as it extends from the image recording unit.
In other words, the effective optical axis in the meaning of the present invention is the section of an optical axis of an image recording unit, (said axis possibly optically deflected multiple times), which intersects the direction of the head of the user without change. The optical axis of the image recording unit corresponds to a line which extends from a center point of an aperture of the image recording unit at a right angle to a plane which comprises the aperture of the image recording unit, the direction of the optical axis of the image recording unit being changeable by optical elements, such as mirrors and/or prisms.
Approximately intersect in the meaning of the present invention means that the effective optical axes have a smallest distance of less than approximately 10 cm, preferably less than approximately 5 cm, especially preferably less than approximately 1 cm. At least approximately intersect therefore means that the effective axes intersect or approximately intersect.
In a further preferred embodiment, in operation, the zero viewing direction of the user is situated essentially parallel to the effective optical axis of at least one of the image recording units. In other words, in the operating state, at least one of the image recording units is situated in such a way that the zero viewing direction of the user may be situated essentially parallel to the effective optical axis of this image recording unit, or the user may position himself in such a way that his zero viewing direction is situated essentially parallel to the effective optical axis of this image recording unit.
In a further preferred embodiment of the present invention, the effective optical axis of at least one of the image recording units is situated essentially parallel to a horizontal direction in the reference system of the earth.
Furthermore, in operation, the horizontal plane of the user is preferably situated in such a way that the effective optical axis of at least one of the image recording units lies therein. I.e., in the operating state of the device of the present invention, at least one of the image recording units is preferably situated in such a way that the user may position himself and/or the user may be positioned in such a way that the horizontal plane of the user comprises the effective optical axis. In the operating state, the user may therefore orient his head in such a way that the horizontal plane preferably comprises the effective optical axis of the image recording unit. The horizontal plane may preferably also be the horizontal plane in the reference system of the earth.
In an especially preferred embodiment, in the operating position, one of the image recording units is situated in such a way that its effective optical axis at least approximately intersects the root of the nose of the user. In other words, in the operating state of the device of the present invention, the user may preferably be positioned and/or position himself in such a way that the effective optical axis of at least one of the image recording units approximately intersects the root of the nose of the user. Approximately intersects means in this case that the minimum distance between the effective optical axis and the root of the nose of the user is less than approximately 10 cm, preferably less than approximately 5 cm, especially preferably less than approximately 1 cm.
In a further preferred embodiment, in the operating position, at least one of the image recording units is situated in such a way that its effective optical axis is situated essentially symmetrically in relation to the pupils of the user. Situated symmetrically in relation to the pupils means in the meaning of the present invention that every point on the effective optical axis has the same distance to both pupils of the user. In other words, the effective optical axis lies in a plane which is situated perpendicularly to a connecting line of the center points of the two pupils and halves this connecting line.
The effective optical axes of the at least two image recording units preferably approximately intersect. In particular the effective optical axes of the at least two image recording units are situated in such a way that a location of minimal distance of the two effective optical axes is at the same distance from both pupils of the user. In particular, a location of minimal distance of the effective optical axes corresponds to the location of the root of the nose of the user. In other words, the effective optical axes at least approximately intersect, the intersection of the effective optical axes and/or the point having minimum distance from the effective optical axes being situated symmetrically in relation to the pupils of the user, preferably corresponding to the location of the root of the nose of the user.
Furthermore, projections of the effective optical axes of the at least two image recording units preferably on a horizontal plane in the reference system of the earth intersect at an intersection angle which is between approximately 10° and approximately 60°, preferably between approximately 15° and approximately 40°, especially preferably approximately 23.5°, by which simplified selection of the user data is achieved.
It is advantageously possible on the basis of the preferred device of the present invention to determine user data of the user even for spectacle frames having very wide bows or for sport spectacle frames, which essentially conceal the eye laterally.
In a further preferred embodiment of the present invention, projections of the effective optical axis of the at least two image recording units on a vertical plane in the reference system of the earth intersect at an intersection angle which is between approximately 10° and approximately 60°, preferably between approximately 15° and approximately 40°, especially preferably approximately 23.5°.
In an especially preferred embodiment of the present invention, in the operating position, the zero viewing direction of the user is situated parallel to the horizontal plane in the reference system of the earth.
Furthermore, the user data determination unit preferably comprises a user data positioning unit, which is designed to assign predetermined user data positions in the two-dimensional space of the image data. In other words, user data, i.e., location information in the three-dimensional space, are imaged on location information in the two-dimensional space. For example, the pupil center point is imaged in the generated two-dimensional image data.
In a further preferred embodiment of the present invention, the user data positioning unit is designed in such a way that the positions in the image data which are assigned to at least one part of the predetermined user data are assignable by a person. For example, delimitations of at least one spectacle lens of the user may be assigned according to a dimensioning in the boxing system by a person.
In a further especially preferred embodiment, the user data positioning unit is designed to predetermine positions of the image data which are assigned to the predetermined user data taking location information of at least one of the image recording units in the three-dimensional space into consideration. According to a preferred embodiment, the assignment of the positions in the image data may be performed by a person. The assignment of the positions is preferably not possible for all existing positions, however, but rather solely for a predetermined selection of positions. For example, the intersection point of a horizontal plane in the reference system of the user with the spectacle lens edges may preferably not be assigned completely along the spectacle lens edges, but rather solely along one or more straight lines in the image data.
In a further preferred embodiment, the user data positioning unit is designed to automatically assign at least one part of the user data to positions in the two-dimensional space of the image data. For example, the positions of the pupils center point may be automatically assigned and/or determined in the two-dimensional space of the image data.
Preferably, the at least two image recording units are designed to generate image data synchronously, the image data recording units especially preferably synchronously generating image data of both eyes of the user.
Furthermore, the image recording units are preferably designed to generate image data of the user sequentially for multiple different viewing directions of the user. For this purpose, for example, image data may be generated for different discrete viewing directions, i.e., discrete deflections of the eyes. However, it is also possible that image data are generated for different discrete head orientations.
In particular, vision behavior of the user may be determined using the data processing device on the basis of the multiple image data. Especially preferably, the image data may be generated in a very rapid chronological sequence using the image recording units, so that the data processing device may determine essentially continuous vision behavior of the user.
According to a further aspect of the present invention, a device for determining optical parameters of a user comprises                at least one image recording unit, which is designed and situated to generate image data of at least sub-sections of the head of the user;        at least one pattern projection unit, which is designed and situated to project predetermined pattern data on at least sub-sections of the head of the user;        a data processing unit having                    a user data determination unit, which is designed to determine user data of at least one sub-section of the head or at least one sub-section of a system of the head and a pair of spectacles of the user situated thereon in the wearing position on the basis of the generated image data, taking the projected pattern data into consideration, the user data comprising location information in the three-dimensional space of predetermined points of the sub-section of the head or the sub-section of the system, and            a parameter determination unit, which is designed to determine at least one part of the optical parameters of the user on the basis of the user data;                        a data output unit, which is designed to output at least one part of the determined optical parameters of the user.        
The device preferably comprises precisely one image recording unit and precisely one pattern projection unit, three-dimensional user data of the sub-section of the head or the sub-section of the system also advantageously being able to be generated according to this aspect of the present invention, analogously to the preceding aspect of the present invention. The three-dimensional user data may advantageously be generated on the basis of image data of only one image recording unit. Preferably, the three-dimensional data are generated using the principle of phase-measuring triangulation. For this purpose, pattern data are superimposed on the head or the sub-section of the head and/or projected thereon using the pattern projection unit. The image recording unit generates image data of the at least sub-section of the head in the two-dimensional space. A surface structure of the sub-section of the head, i.e., the coordinates in the third dimension, is generated by phase information of the projected pattern data indirectly via intensity patterns.
As a result, according to this aspect of the present invention, three-dimensional user data may be generated. The optical parameters of the user may be determined on the basis of the three-dimensional user data analogously to the preceding aspect of the present invention, only one image recording unit being used.
The pattern projection unit is, for example, a typical projector such as a commercially available video projector. The projected pattern data are, for example, a striped pattern or a binary sinusoidal pattern. The pattern data are projected on at least one sub-section of the head of the user and image data are generated therefrom using the image recording unit. Image data are generated at a triangulation angle by the image recording unit from the sub-section of the head of the user thus illuminated. The triangulation angle corresponds to the angle between an effective optical axis of the image recording unit and a projection angle of the pattern projection unit. Height differences of the sub-section of the head correspond to lateral displacements of the stripes of the striped pattern as the preferred pattern data, for example. Preferably, the so-called phase shift method is used in the phase-measuring triangulation, a periodic wave pattern which is approximately sinusoidal in the intensity distribution being projected on the sub-section of the head and the wave pattern being moved step-by-step in the projector. During the movement of the wave pattern, image data are preferably generated at least three times by the intensity distribution (and the sub-section of the head) during one period. The intensity distribution may be concluded from the generated image data and a phase position of the image points to one another may be determined, points on the surface of the sub-section of the head being assigned to a specific phase position in accordance with their distance from the image recording unit. Furthermore, reference is made to the academic thesis having the title “Phasenmessende Deflektometrie (PDM)—ein hochgenaues Verfahren zur Vermessung von Oberflächen [Phase-Measuring Deflectometry (PDM)—a High Precision Method for Measuring Surfaces]” by Rainer Seβner, March 2000, which represents an integral part of the disclosure of the present application for further definitions of terms.
A further aspect of the present invention is to provide a method for determining optical parameters of the user having the following steps:                generating image data of at least sub-sections of the head of the user from at least two different recording directions;        determining user data of at least one sub-section of the head or at least one sub-section of a system of the head and a pair of spectacles of the user situated thereon in the wearing position on the basis of the generated image data, the user data comprising location information in the three-dimensional space of predetermined points of the sub-section of the head or the sub-section of the system;        determining at least one part of the optical parameters of the user on the basis of the user data, and        outputting at least one part of the determined optical parameters of the user.        
Two different recording directions is understood in the meaning of the present invention to mean that different image data are generated of overlapping sub-sections of the head, preferably of the same sub-section of the head, in particular that image data of identical sub-sections of the head of the user is generated from different perspective views. As a result, the same sub-section of the head is imaged, but the image data differ. Different recording directions may also be achieved, for example, in that the image data are generated by at least two image recording units, effective optical axes of the at least two image recording units not being parallel.
In a preferred embodiment variation of the method of the present invention, at least one pupil is completely imaged in the generated image data.
Furthermore, at least one pupil of the user and a spectacle frame edge and/or a spectacle lens edge is preferably imaged in the generated image data, the at least one pupil of the user being enclosed by the spectacle frame edge and/or the spectacle lens edge in the generated image data.
According to a further aspect of the present invention, a computer program product having program parts is provided which, when loaded in a computer, is designed for executing the method according to the present invention.
The present invention is described for exemplary purposes in the following on the basis of the attached drawings of preferred embodiments.